IEEE 802.11ac supported MU transmission using spatial degrees of freedom via MU multiple-input multiple-output (MIMO) in the downlink (DL) direction from the access point (AP) to the stations (STAs). To improve performance, IEEE 802.11ax is considering adding orthogonal frequency division multiple access (OFDMA) alongside MU-MIMO in the downlink as well as the uplink direction where transmission is from STAs to the AP.